This disclosure relates to a method and apparatus for converting a call from one network to a femtocell. More particularly, this disclosure relates to a method and apparatus for a hand-off from a macrocell to a femtocell or other small base station models in an Internet protocol Multimedia Subsystem (IMS) network.
While the disclosure is particularly directed to voice and network transfer and thus will be described with specific reference thereto, it will be appreciated that the disclosure may have usefulness in other fields and applications. For example, this disclosure may be used in a variety of data transfer systems and methods in order to support gradual migration from one network to another, thereby allowing service provides to invest their time and energy in future IMS technology.
By way of background, Code Divisional Multiple Access (CDMA) mobiles are in use all over the world. Many people use mobile stations in order to transfer voice and data through a well established radio network. Currently, there are many known methods for converting voice path handoffs across the CDMA radio network.
The IMS/Session Initiation Protocol (SIP) based network is a network with an internet backbone that supports many types of voice and data transfer. Examples of this kind of transfer include Voice-over Internet Protocol (VoIP). Although VoIP technology is less commonly used than other types of voice transfer, it is gaining popularity throughout the world.
Currently in the industry, there is no effective way to convert a 3G1x signal that originates or is intended for the CDMA network to an IMS network.
One major difficulty in finding a solution to a CDMA mobile migration from a CDMA based network to an IMS network involves the difficulty of a hand-off application server finding the correct femtocell to hand off to. For example, when transferring from one macrocell to another, the hand-off is simplified because there are very few possible cells within a certain distance which allow a hand-off to take place. However, with femto cells there are many cells within or adjacent to a macrocell. Thereby it is difficult to find the correct femtocell. Unfortunately, there are not enough Pseudorandom Number (PN) offsets for each femtocell to have a unique PN offset. Even using a neighbor list which will only include relatively nearby femtocells there are still too many femtocells within the predetermined radius to give each femtocell their own pseudo random number offset.
Therefore there is a need in the industry to supply a data network and allow for IP awareness to take place on the CDMA network. There is also a need in the industry for a method which will allow a handoff application server to accurately find the correct femtocell which should be receiving the hand-off for any particular mobile station.
There is also a need in the industry to allow IMS network coverage and capacity to be extended to signals originally made over other networks. There is further need for these transfers to be converted and received on an IMS network and managed through a seamless means. There is also a need for a method to allow hand-offs from a CDMA network to an IMS network.
The present disclosure contemplates a new and improved system and method that resolves the above-referenced difficulties and others.